Deposition of a metallic coat on metal surfaces



United States Patent 3,294,578 DEPOSITION OF A METALLIC COAT 0N METAL SURFACES Stanley P. Popeck, Nimmonsburg, N.Y., assignor to General Aniline & Film Corporation, New York, N.Y., a corporation of Delaware No Drawing. Filed Oct. 22, 1963, Ser. No. 318,102

6 Claims. (Cl. 117-130) This invention relates to a new and novel process of depositing a metallic coat on metallic surfaces.

I have discovered that cations of copper, gold, palladium, platinum, silver and te-llurium derived from a compound containing an anion such as oxide, hydroxide, carbonate, chloride, bromide, iodide, etc., form complexes with certain nitrogen containing compounds in the presence either of hydrobromic or hydroiodic acid. These complexes deposit the metal cation of the complex when in contact with a metal which is aboxe the complexed metal cation in the electromotive series including alloys thereof such as yellow brass, soft iron, stainless steel, bronze, and the like. The unusual feature of applying these complexes is that they give a hard plating or coating of the metal without resorting to an electrical current. The plating of metals with the complexes is so rapid that within seconds a metallic coating is observed whereas within seconds a durable plate is deposited at a temperature ranging from ambient to 100 C. The most outstanding feature is that there is no need to degrease the metal to be plated and in fact no buffing or polishing prior to plating is necessary. The silver and gold plate, however, may be polished with finely pulverized sodium bicarbonate, calcium carbonate or other common polishing agent such as diatomaceous earth.

The nitrogen containing compounds which may be employed to form the complexes are characterized by the following formulae:

(1) H20GH2 H2C\ /C=O N i N R R1 R1C ON/ and wherein R and R represent either hydrogen or an alkyl of from 1 to 4 carbon atoms, and R and R represent an alkyl of from 1 to 4 carbon atoms.

As examples of nitrogen containing compounds of the foregoing formulae, which are used as such or in admixture for complexing with compounds containing the aforementioned metal cations, the following are illustrative:

2-pyrrolidone 5-methyl-2-pyrrol-idone N-methyl-Zpyrrolidone N-ethyl-Z-pyrrolidone N-isopropyl-Z-pyrrolidone N-butyl-Z-pyrrolid-one N,N-dimethyl formamide N,N-diethyl formamide N,N-dipropy-l formamide N,N-disopropyl formamide N,N-dibutyl formamide N,N-dimethyl acetamide N,N-diethyl acetamide N,N-dipropyl acetamide N,N-dibutyl acetamide N,N-dim'ethyl propi-onamide N,N-diethyl propion'amide N,N-dipropyl propionamide N,N-dibutyl propionamide N,N-dimethyl butyramide N,N-diethyl butyramide N,N-dipropy'l butyramide N,N-dibutyl butynamide Aniline N-dimethyl aniline N-diethyl aniline N-dipropyl aniline N-dibutyl aniline Dimethyl amine Diethyl amine Dipropyl amine 1 Dibutyl amine Trimethyl amine Triethyl amine Tripropyl Iamine Tributyl amine In addition to the foregoing, I found that pyridine,, pyrrole, pyr-ro'l-ine, py-rrolidine, pyrimidine, quinoline, etc. as well as mixtures thereof are also useful in forming the complexes.

In forming the complex, where the halides of the aforementioned metals are used, one mode of the metal halide is treated at room temperature with one mole in excess of the nitrogen containing compound in liquid form to cover the solid halide salt followed by the addition of one mole of either hydrobromic or hydroiodic acid. The copper and gold halides may be either in their ous or ic form. After stirring for a few minutes at room temperature, until solution is reached, one part by weight of the resulting solution of the complex is then added to 1-4 parts by weight or volume of the nitrogen containing compound which may be the same as initially employed or any one or a mixture of the above enumerated compounds. In the event the nitrogen containing compound is a solid at room temperature a mole thereof in excess is used to cover the solid halide salt followed by the addition of either the hydrobromic or hydroiodic acid with stirring. The mixture during stirring is heated at a temperature ranging from 35 C. to C. until a solution is reached. One part by weight of the resulting solution is then added to 1-4 parts by weight or volume of the nitrogen containing compound which, if a solid, had been preheated into liquid form. The resulting solution is then used for plating. During plating the solution may be gently heated to maintain it in liquid form.

Where oxides, hydroxides, carbonates and salts other than halides of the aforementioned metals are used in the preparation of the complex one mole thereof is treated at room temperature with one mole of either hydrobromic or hydroiodic acid' with stirring for a few minutes until a solution is formed. At this time one mole in excess of the nitrogen containing compound is added with stirring followed by the addition of 0.5-1.0 mole of either hydrobromic or hydroiodic acid with or without the addition of a small amount of water. After stirring for a few minutes, usually 5-10 minutes, one part by weight of the resulting solution of the complex is then added to 14 parts by weight of either water or of the nitrogen containing compound which may be the same as initially employed or any one or a mixture of the above enumerated compounds.

In the case of silver, instead of employing either one of the individual halides such as chloride, bromide or iodide to form the silver complex, I have found that a mixture of silver bromide and silver iodide gives excellent deposits of metallic silver. The ratio of silver bromide to silver iodide is immaterial so long as the mixture constitutes one mole of the silver salts.

The following examples will illustrate the preparation of the complexes and their use in plating the various metallic surfaces. It is to be clearly understood that these examples are merely illustrative and are not to be construed as being limitative. All parts given are by weight unless otherwise stated:

Example I 20 grams of silver bromide were first treated with 20 ml. of dimethyl formamide, enough to cover the solid. Then was added 20 ml. of 48% hydrobromic acid. After stirring a short while the volume was made up to 100 ml. with dimethyl formamide.

Example II 15 grams of silver iodide was first treated with 15 ml. of N-methyl-Z-pyrrolidone to cover all of the solid. 25 cc. of .48% hydrobromic acid was slowly added. After stirring awhile 'a paste was formed which was diluted to 100 ml. with N-methyl-Z-pyrrolidone and stirred until dissolved.

Example III 15 grams of silver bromide was mixed with grams of silver iodide; this was covered with 20 ml. of dimethyl acetamide. After stirring a few minutes, 20 ml. of 48% hydrobromic acid was added and stirred a few minutes. Enough dimethyl acetamide was added to bring the volume to 100 ml. with stirring until dissolved.

Example IV To 50 mg. of sodium gold chloride was added 0.5 ml. of dimethyl propionamide. After stirring for one minute 1 ml. of hydroiodic acid (58.7%) was added and stirring continued for an additional minute. 3 ml. of dimethyl propionamide was added and after two minutes of stirring the solution was ready for the plating process. Gold was deposited from this solution on copper and on silver at about 88 F. (31 C.). The presence of a small amount of chromium ion in the plating solution enhances and accelerates the gold plating.

Example V To 50 mg. of palladium chloride was added 0.5 ml. of dimethyl butyramide. 0.5 cc. of 48% hydrobromic acid was added, solution occurred almost immediately. After a few minutes of stirring, 3 cc. of dimethyl butyramide was added and stirred for a few minutes. The plating of copper and stainless steel was carried out at a temperature of 6570 C. yielding a shiny coat on both metals.

Example VI To 0.2 gram of tellurium oxide was added 2.0 cc. of 48% hydrobromic acid. Upon stirring for a few minutes solution occurred. At this time cc. of dimethyl formamide was added. After a minute of stirring 10 cc. of

water was added followed by 1 cc. of 48% hydrobromic acid with stirring for 5 minutes. Water was then added in 25 cc. portions until a total volume of 200 cc. was reached.

Example VII To 1 gram of cuprous chloride was added 5 m1. of dimethyl formamide. After a few minutes of stirring, 5 ml. of 48% hydrobromic acid was added. Stirring was continued while the solution of the complex was diluted to 25 ml. with dimethyl formamide.

tained.

4 Example VIII A piece ofcopper without any pretreatment such as degreasing or bufling was placed into the plating solution of Example II for 10 seconds, removed, washed with water and rubbed with sodium bicarbonate to form a shiny silver coating.

ExampleX A piece of copper without any pretreatment such as degreasing or bufling was placed into the plating solution of Example 111 for 10 seconds, removed, washed with water and rubbed with sodium bicarbonate to form a shiny silver coating.

Example XI A piece of yellow brass was placed in the plating solution of Example I for 30 seconds, removed, washed with water and rubbed with sodium bicarbonate to give a shiny silver plate.

Example XII A piece of bronze was placed in the plating solution of Example 11 for 30 seconds, removed, washed with water and rubbed with sodium bicarbonate to give a shiny coating of silver.

Example XIII Example IV was repeated with the exception that dimethyl propionamide was replaced by an equivalent amount of N-dimethyl aniline and the same results 0b- Example XIV Example V was repeated three times with the exception that dimethyl butyramide was replaced by an equivalent amount of dibutyl amine, tributyl amine and pyridine, respectively, with the same results.

Example X V' A small flat piece of aluminum A by 1 /2" and %4" thick was placed in the plating solution of Example VII and heated on a steam bath for 2 minutes, removed, washed with water and rubbed with sodium bicarbonate to form a shiny copper coating.

The various individual complexes prepared as above are compatible with each other and deposit an alternate layer of metals on the metallic surface being plated. For example, equal parts of the gold and silver complexes when mixed together and a piece of copper placed into the mixture, a layer of silver and gold is deposited on the copper surface within a few minutes. It appears that the silver plates the copper first and the gold then deposits on the silver.

It is to be noted that the presence of a small amount of chromium ion also enhances and accelerates the plating of gold on silver as well as on copper. Any metal coated with copper can then be plated with gold, palladium or silver. Any metal plated with silver can then be plated with gold or palladium.

Iclaim:

1. The process of depositing a metallic coat on a metallic surface without resorting to an electric current which comprises contacting said surface with a solution of a coating complex obtained by dissolving one mole of a compound containing a cation selected from the class consisting of copper, gold, palladium, platinum, silver and tellurium in one mole in excess of at least one nitrogen containing compound selected from the group consisting of compounds having the following general formulae:

( HzC-OH2 N r r R1CON and 2)3 wherein R and R represent a member selected from the group consisting of hydrogen and alkyl group of from 1 to 4 carbon atoms and R and R represent an alkyl group of from 1 to 4 carbon atoms, and in one mole of an acid selected from the class consisting of hydrobromic and hydroiodic.

2. The process according to claim 1 wherein the cation is silver.

3. The process according to claim 1 wherein the cation is palladium.

4. The process according to claim 1 wherein the cation is tellurium.

5. The process according to claim 1 wherein the cation is copper.

6. The process according to claim 1 wherein the cation is gold.

References Cited by the Examiner UNITED STATES PATENTS 3,250,784 5/1966 Gensheimer et a1. 117130 X ALFRED L. LEAVITT, Primary Examiner.

R. S. KENDALL, Assistant Examiner.

Disclaimer 3,294,578.Stanley P. Popeck, Nimmonsburg, N.Y. DEPOSITION OF A ME- TALLIC COAT ON METAL SURFACES. Patent dated Dec. 27, 1966. Disclaimer filed Sept. 30, 1982, by the assignee, Eastman Kodak Co.

Hereby enters this disclaimer to all claims of said patent.

[Official Gazette February 8, 1983.] 

1. THE PROCESS OF DEPOSITING A METALLIC COAT ON A METALLIC SURFACE WITHOUT RESORTING TO AN ELECTRIC CURRENT WHICH COMPRISES CONTACTING SAID SURFACE WITH A SOLUTION OF A COATING COMPLEX OBTAINED BY DISSOLVING ONE MOLE OF A COMPOUND CONTAINING A CATION SELECTED FROM THE CLASS CONSISTING OF COPPER, GOLD, PALLADIUM, PLATINUM, SILVER AND TELLURIUM IN ONE MOLE IN EXCESS OF AT LEAST ONE NITROGEN CONTAINING COMPOUND SELECTED FROM THE GROUP CONSISTING OF COMPOUNDS HAVING THE FOLLOWING GENERAL FORMULAE: 